It has been a long debated topic how much protein a person can digest at any one time. Nutritionists and doctors have maintained for decades that "people can only digest 30 grams at a time of protein and any additional protein is wasted or converted to fat." So say the powers that be.

Now, I wish I could examine the study or research they are basing this advice on so I could dispute it but I can't. Why you ask? Because in all my years of searching the medical data banks, talking to researchers, and falling asleep in the medical library after hours of reading, I have been unable to find exactly where this advice comes from or what it's based on.

At one time, I went so far as to offer a reward to anyone who could show me a recent study that showed that 30 grams of protein was the upper limit anyone could digest, regardless of age, weight, and activity levels.

Why is it 30 grams? Why not 28 or 35? Are we saying that the digestive and absorptive abilities of a 285 pound 23 year old football player is the same as a 50 year old 115 pound women?

Now digestion is a very complex topic. Many people think you eat some protein, it mixes with some acid or something, gets broken down into amino acids, gets taken up into the body, and everyone is happy.

I wish it were that simple. As with all foods, the breakdown of protein starts in the mouth with the simple chewing of food and the exposer to certain enzymes. In the stomach, food mixes with enzymes and other factors such as lipase, pepsin, intrinsic factor, and of course HCL (stomach acid).

It moves onto the small intestine and then the large intestine.The small intestine is considered the major anatomical site of food digestion and nutrient absorption and is made up of section such as the duodenum, jejunum, and the ileum. Pancreatic enzymes (chymotrypsin, trypsin, etc.), bile salts, gastrin, cholecystokinin, pepidases, as well as many others factors are released here.

The large intestine is composed of the ascending colon, transverse colon, descending colon, and the sigmoid colon, which all play a part in absorbing the nutrients we eat. Sound complicated? It is. Believe me, I am leaving out a great deal of information so you wont fall asleep reading my little column! Suffice it to say, digestion is a very complicated thing and there are many places along the chain of digestion that can both enhance and degrade a persons ability to absorb the foods we eat.

There is no reason to think that among this complicated process that there are not wide individual differences in a persons ability to digest and absorb protein. For some person who is inactive, elderly, and for what ever reason lives with compromised digestion, 30 grams of protein at one sitting might very well be too much for them to handle.

By the same token, assuming a 220lbs healthy athlete is unable to exceed 30 grams of protein in one sitting is neither proven by medial science or even logical in my view. So what if the 30 gram rule turns out to be true? If we examine some of the more recent studies on the protein requirements of athletes done by researchers from both the United Sates and Canada , we come to some recommended protein intakes that far exceed the RDAs, some times by as mush as 225%!

These researchers came to the conclusion that protein intakes for athletes should range from approximately 1.2 grams of protein per kilogram of bodyweight for endurance athletes and up to 1.8g of protein per kg for strength training athletes. For a 200 pound bodybuilder-a strength training athlete-that would be approximately 164 grams of protein per day (most bodybuilders I know eat considerably more protein per day, but that's for another fight and another article...). Assuming that 30 grams of protein is the most anyone can digest, absorb, and utilize, this person would have to split his intake into about five meals (164 divided by 30 = 5.47). So, given the advice by many people that 30 grams is all anyone can digest at a single sitting, it appears a person can achieve the goal of 30 grams of protein per meal even with the higher intakes recommended in the modern research (assuming they are willing or able to eat five meals per day).

However, if you happen to eat more than that per meal as a healthy athlete I don't think you have anything to worry about. I wont tell anyone. Me, I would suggest you stick to the one gram per pound of bodyweight rule, which often exceeds the research mentioned above. Also, read the "Protein Myth" article at the BrinkZone site for more info on this topic.

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If you act sanctimonious I will just list out your logical fallacies until you get pissed off and spew blasphemous remarks.

Yeah. I have to wonder where that number came from. I'll bet it was from an early generation protein supplement company, who upon failing to get more than 30 grams into 3 or 4 scoops of their caveman like product proclaimed that this was the upper limit and hence the number they chose.

good article. it could be that 30 grams of protein at one meal sounded reasonable, so nutritionists started using that. i personally don't believe that a specific number could be used to describe anything related to defining the complex human body.

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it could be that 30 grams of protein at one meal sounded reasonable, so nutritionists started using that.

You know, you're absolutely right. It could have also have been an offhand comment by a very respected nutritionist or something one wrote in a book. I just read a very interesting research review (or lack thereof) on the whole H2O 8x8 thing. We've all heard it. Eight ounces of water eight times a day. Now of course we need lots of liquid but it turns out there is NO actual research or physiological basis for this advice in normal healthy people. As far as the reasearchers could tell it was just some comment that got taken out of context and adopted as the prevaling wisdom. Likely something like that could have happened with the thirty grams protein thing.

Great post... very logicially thought out... you are a one to be heard... personally I have never really believed this "myth" and stuck to the idea that downing 40-60 grams each time is good for me... I have seen results from doing this... but I couldn't nor would I venture to guess just how much my body adsorbs... it would be rather foolish to even estimate... but I know that I'm downing at least 300-400 grams every day... how much gets to my muscles... who really knows... but keeping my body in a postive nitrogen balance is something that I strive for...

I couldn't agree more. In the end all that counts is you meat your protein goals. If that means more at once so be it. Most of us err on the side of more just in case anywayt. It'll either be utilized, oxidized, stored, or pooped out. Digestion is too complicated to try and pin down.

Bodybuilding, more so than any other sport, seems to have developed many myths that people cling to so strongly thatthey're accepted as FACT even though there may be little or no scientific evidence supporting these myths. Protein mightpossibly have more ill-founded myths surrounding it than any other subject, probably because it plays such a large role inany nutrition program focused on building muscle. Well, the myths shall spread no further: let the debunking begin!

Myth: "You can only absorb &lsquo;X' grams of protein in one meal."

The real deal: Not only is this myth not rooted in any kind of fact, it's actually a misnomer in and of itself. Absorption refers to the amount of a certain substance that makes it into circulation (blood) from the digestive tract. The body will absorb a good portion of the protein you eat regardless of the amount of protein in the meal (though there's a limit to the percentage absorbed and it will vary between protein sources). What this myth actually refers to is protein/amino acid utilization. Specifically, what's the maximum amount of protein at a meal that will be used for muscle-building processes, and at what point does the amount of protein become excessive and the extra amino acids burned for energy rather than retained? At this point, researchers have no good answer to this question, but the answer probably depends on many various factors, including but not limited to:

- lean body mass

- length of time since last protein-containing meal

- amount of protein at previous meal

- type of protein source

- training state (Post-workout? Pre-workout? Resting?)

- total calories in the meal

- caloric balance

Although there's no definitive answer as to the maximum amount of protein that's beneficial at a meal, there's some research out there that is mildly helpful. Leucine, the amino acid that's an anabolic component of protein1 and is responsible for stimulating protein synthesis, was administered at different doses in rats to see what dose elicited the maximum protein synthetic response.2 The researchers found that the maximum beneficial dose of leucine was achieved at 0.68 grams of leucine per kilogram of bodyweight. This equates to about 62 grams of leucine in a 200-pound individual, which is an unrealistic amount to get from whole food.

There are many problems with applying the absolute numbers from this study to a whole food meal in humans because of the differences in protein metabolism between rats and humans. In order to determine what level of leucine at a meal elicits the greatest anabolic response for the longest period of time more human studies will be required, but the research is moving in the right direction. While there's most definitely a maximum beneficial protein intake at a meal, no studies have directly addressed the subject and the number is likely to be influenced by various factors. So, pay no attention to Joe Dumbbell who says you can only absorb (insert gram amount) of protein at a meal, because he has no clue.

The real deal: An incomplete protein source is defined as a food lacking in one or more amino acid. I believe this myth came about in response to research that concluded that when certain amino acids are deficient in the diet, skeletal muscle protein synthesis can be inhibited.3,4 This is very unlikely to be a problem for the typical bodybuilder as the condition would only manifest itself if he or she ate a diet that was predominately based on a certain food that was deficient in an amino acid over a few days, not meal to meal. Additionally, most bodybuilders consume a complete source of protein at almost every meal because any animal product will contain the complete spectrum of amino acids.

Even if one consumed an incomplete protein source at a meal there's no way a decrease in protein synthesis would occur so long as a complete protein source was consumed with this meal. One should therefore absolutely count incomplete protein sources toward their total protein intake since they're consuming the full spectrum of amino acids over the range of their entire diet.

Myth: "High-protein diets are hard on the kidneys."

Quite a few medical professionals have theorized that a high-protein diet may be hard on the kidneys since a highprotein diet increases the body's production of ammonia, which must be excreted by the kidneys as urea. As a result, lowproteindiets have typically been recommended to people who suffer from renal disorders. However, the notion that a high-protein diet is hard on the kidneys in a healthy person is a big stretch. Researchers who recently conducted a review of the available scientific literature on the subject concluded that "no significant evidence exists for a detrimental effect of high protein intakes on kidney function in healthy persons." 5

Additionally, a study examining bodybuilders with protein intakes of 2.8 grams per kilogram vs. well-trained athletes with moderate protein intakes revealed no significant differences in kidney function between the groups.6 It's therefore reasonable to conclude that a high-protein diet is NOT hard on the kidneys.

Myth: "Don't take your creatine with protein because protein contains glutamine and glutamine competes with creatine for the same transporter!"

The Real Deal: There's not an ounce of truth to this. Creatine and glutamine have completely different receptors.Creatine transport into skeletal muscle is regulated by the Creatine Transporter7 while glutamine transport into skeletalmuscle is regulated by a system known as "System Nm." 8 The only thing these transporters have in common is thatthey are both sodium-dependent transporters, meaning that they use differences in sodium concentrations across thecell membrane to drive creatine into cells. Apparently somewhere along the line, somebody believed that since glutamineand creatine transporters both shared that characteristic, they must be the same transporter and the myth spread fromthere. Let the confusion end here: they do not share the same transporter, and taking protein/glutamine with creatinewon't decrease creatine uptake into muscle.

Myth: "The more protein you take the better."

The real deal: There's little doubt that increasing one's protein intake is beneficial in achieving optimal anabolism, butsome people have taken "high protein" to the extreme. Protein intakes of 2 grams per pound and even 3 grams perpound have been suggested by various trainers who believe that there's no upper limit to the anabolic effects of protein.Unfortunately, the available scientific evidence doesn't agree with their views. As protein intake increases, the bodyincreases its production and activity of enzymes that break down and burn amino acids for energy.9,10

In fact, there's some evidence that very high protein intakes may actually decrease protein synthesis when compared to more moderate protein intakes.11 (Editor's Note: This study was conducted on endurance athletes, so it may not apply to strength-power athletes - AM.) It appears from a review of the scientific literature that there's little anabolic benefit to protein intakes over 1gram per pound of bodyweight.12,13 While on a calorie-restricted diet, increasing protein intake may have additional muscle-sparing benefits14 however, it may be wise to increase protein intake to 1.25-1.5 grams per pound of bodyweight.

Hopefully this article has helped clear up some confusion surrounding high protein diets. I fear the spread of misinformationwon't end however, so it's everyone's responsibility not to be so quick to believe everything they hear or read. Keep in mind, if someone makes a claim they can't support with established scientific evidence, there's a good reason...they likely have none.